1. Field of the Invention
The present invention relates to semiconductor packaging. In particular, it is related to a package substrate and a flip chip mounted semiconductor device.
2. Description of the Related Art
Conventionally, a flip chip mounted semiconductor package includes either a ceramic substrate or resin substrate, which is used as a package substrate for wiring to mount a semiconductor chip. A semiconductor chip is connected to the package substrate via flip chip connection bumps made from soldering balls, and in order to protect that connection area, thermosetting resin, which is called underfill resin, is filled thereto. On the surface of the package substrate there are formed external connection electrodes for making electrical connections with the mounting substrate, so as to provide a connection with the package substrate via ball grid array (BGA) balls, which are soldering balls mounted on these external connection electrodes. A feature of the flip chip mounted semiconductor package is that the respective connecting portions of the flip chip connector and the BGA connector are each sandwiched with differing materials. In other words, the flip chip connector is generally sandwiched between a semiconductor chip made from silicon and a package substrate made from a ceramic or a resin. Also, the BGA connector is sandwiched between the package substrate and a mounting substrate generally made from fiber-reinforced resin such as FR-4.
It has been verified that decreases in the yield of conventional flip chip mounted semiconductor devices are mainly caused by damage due to the difference in thermal expansion between a semiconductor chip and the package substrate.